Content protection technology is about content and usage rules encryption, usage rules binding to content and usage rules enforcement. Usage rules govern permissions and restrictions applying to events or content handling, such as consuming, copying, and moving.
By “content”, it is meant hereafter any digital media object subject to usage rules and which has a commercial value.
Content protection technology (CPT) applies to management of content in an authorized domain (an extension of the home network including mobile and remote devices). Content is encrypted and cryptographically bound to a Content License (CL) embedding usage rules.
Such features as rental periods, simultaneous viewing control and remote access permission make possible advanced business models as well as flexible content handling by users.
One may use CPT to consolidate the existing CAS business model. A typical example is provided by the broadcast of a high commercial value movie. The CAS has a mean to sell a product giving access to the corresponding content on a per-event basis, called Pay-Per-View (PPV) or Video-on-Demand (VOD). Knowing this event will be acquired as content under content protection technology in the user domain, we will use usage rule to forbid copy of the movie, but grant remote access (so the user can order the event in advance and consume it at any place when it is broadcast). This is a natural reinforcement of the initial concept of PPV or VOD to the user domain.
A complementary example is provided by the broadcast of sport-event channel. The CAS has a way to sell a product giving access to the channel, called subscription. A natural reinforcement of the initial concept is to forbid remote access during broadcast, but allow copying (since the value of sport event lies in the fact it is a live event), and allow remotely accessing the record once the event is past.
The technical means to propagate these extended concepts of PPV, VOD or subscription events in the user domain is to securely signal usage rules with the CAS Entitlement Control Messages (ECM), and implementing ECM-to-content license translation.
This solution has several drawbacks. One of them comes from the fact that the usage rules can be quite big. Thus, introducing a usage rule in an ECM requires changing the size of the ECM. This implies that receivers must be updated for being able to process these ECMs. This also implies that bandwidth is used to send ECM rather than valuable content. All these characteristics imply that complex rules cannot be used in such a system.
Another drawback of this solution is that one has to signal several usage rules if several content protection technologies must be targeted in the home network. This also limits the complexity of the rules and the number of usage rules that can be implemented.
The specification of addressed content protection technology may evolve. In case one uses a third party technology (e.g. standard technology), this evolution is not controlled by the management center. The evolution may imply modifications in the entitlement control message format. The modifications should be made independently from the management center.